How to use npx to run MCP servers without installing

npx comes bundled with Node.js (specifically with npm 5.2+). Open your terminal and run npx --version to confirm it is available. If you see a version number, you are good to go. If you get command not found, you need to install or update Node.js. On macOS with Homebrew, run brew install node. On Windows, download from nodejs.org.

1# Check npx is available
2npx --version
3# Should output something like: 10.2.4
4
5# If not found, check Node.js installation
6node --version
7npm --version

When npx runs a package for the first time, it prompts the user to confirm the installation. In an MCP server context, there is no terminal to answer this prompt, so the server hangs silently. The -y flag auto-confirms the installation. Always include -y in your args array right after npx. This is the single most important thing to remember when using npx with MCP servers.

1// claude_desktop_config.json
2{
3  "mcpServers": {
4    "github": {
5      "command": "npx",
6      "args": ["-y", "@modelcontextprotocol/server-github"],
7      "env": {
8        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_your_token"
9      }
10    }
11  }
12}

On Windows, GUI applications like Claude Desktop and Cursor do not inherit the shell PATH, so they cannot find npx directly. The fix is to use cmd as the command and pass /c npx as arguments. This launches a cmd.exe shell that resolves npx from the system PATH. This is the most common cause of 'server not found' errors on Windows.

1// Windows — claude_desktop_config.json
2{
3  "mcpServers": {
4    "github": {
5      "command": "cmd",
6      "args": ["/c", "npx", "-y", "@modelcontextprotocol/server-github"],
7      "env": {
8        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_your_token"
9      }
10    }
11  }
12}
13
14// macOS/Linux — no wrapper needed
15{
16  "mcpServers": {
17    "github": {
18      "command": "npx",
19      "args": ["-y", "@modelcontextprotocol/server-github"],
20      "env": {
21        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_your_token"
22      }
23    }
24  }
25}

If npx still cannot be found (common on macOS when using nvm or Homebrew), use the absolute path to npx instead of relying on PATH resolution. Run which npx (macOS/Linux) or where npx (Windows) in your terminal to find the full path. Replace the command value with this absolute path. This bypasses all PATH resolution issues.

1# Find absolute path to npx
2which npx
3# Example output: /opt/homebrew/bin/npx
4
5# Use absolute path in config
6{
7  "mcpServers": {
8    "github": {
9      "command": "/opt/homebrew/bin/npx",
10      "args": ["-y", "@modelcontextprotocol/server-github"],
11      "env": {
12        "GITHUB_PERSONAL_ACCESS_TOKEN": "ghp_your_token"
13      }
14    }
15  }
16}

Some npx-based MCP servers accept additional command-line arguments after the package name. Add these to the args array after the package name. For example, the filesystem server takes directory paths as arguments to specify which directories it can access. If you run into configuration challenges with multiple servers or complex argument setups, the RapidDev team can help you design an optimal MCP configuration.

1{
2  "mcpServers": {
3    "filesystem": {
4      "command": "npx",
5      "args": [
6        "-y",
7        "@modelcontextprotocol/server-filesystem",
8        "/Users/yourname/projects",
9        "/Users/yourname/documents"
10      ]
11    }
12  }
13}